Electric lamp for mixed light



Nov. 29, 1960 J. BUSER ELECTRIC LAMP FOR MIXED LIGHT 3 Sheets-Sheet 1Filed July 25, 1956 INVENTOR: Johann Buser' BB ouwa g ATTORNEQS Nov. 29,1960 J. BUSER ELECTRIC LAMP FOR MIXED LIGHT Filed July 25, 1956 3Sheets-Sheet 2 53 HIHI Fig. 4

INVENTOR: J h nr BUS 1 ATTORNEHS Nov. 29, 1960 J. BUSER ELECTRIC LAMPFOR MIXED LIGHT Filed July 25, 1956 3 Sheets-Sheet 5 INVENTOR. JohannBose/- BY @Mk w ATT O\1NE$5 ELECTRIC LAMP FOR MIXED LIGHT Basel,Switzerland, assignor to Buser-Lampen A.G., Riehen, land, a Swisscompany Filed July 25, 1956, Ser. No. 599,953

'3 Claims. (Cl. 315-46) The present invention relates to a mixed lightlamp for the simultaneous production of mercury-vapor are light andincandescent light, which lamp consists of a super high pressure burnerand a filament.

It has been shown that in lamps of the aforesaid type the temperature ofthe filament at the moment the lamp is switched on is quitesubstantially higher than in the normal operating condition. An economiclight yield can thus only be obtained from the filament if thetemperature in the stationary operating state reaches a levelcorresponding to the desired and admissible light efficiency. If thiscondition is fulfilled, the temperature of the circular-coil filament isquite substantially superelevated in the heating up stage, which impairsthe lamps useful life. In order to give the lamp a reasonably longuseful life, one would be compelled to have recourse, albeit not to thesame extent, to the same means as are used in the construction of mixedlight lamps with luminous elements connected in series; in other words,a compromise would have to be made which would mean nothing other than aloss of light efficiency in favour of longer lamp life. In view of thesesymptoms of disintegration and destruction which interact as a result ofmany different influences, the irregularity will become an incalculableproblem.

According to the invention this difficulty of producing a mixed light bymeans of a mixed light lamp, such as for instance the one disclosed inUS. Patent No. 2,669,676, is overcome by magnetically coupling thecircuit of the filament, which receives approximately mains voltage, tothe discharge circuit of the burner by means of a series connection toone winding section of the electric arcs stabilizing impedance, wherebya superelevation in the temperature of the filament when the lamp isswitched on cannot result from the low gas pressure in the lamps mainvessel at this moment because of the initially low voltage at theelectric arcs.

In mains with voltages of more than 220 volts a current limiting chokeconsisting of several Winding sections is used to limit the current orstabilize the electric arc, and, according to the invention, thefilament is connected in series to one winding section of this currentlimiting choke. In the case of single-phase alternating currentoperation current limiting chokes whose winding sections are preferablyelectrically interconnected in series are used for this purpose.

The endeavour is made for known reasons to operate the filament with aslow a supply voltage as possible. In contradistinction hereto,mercury-vapor high and super high pressure lamps can be operatedeconomically only at a supply voltage of 220 volts and over. For thesereasons the production of a mixed light according to the invention isparticularly suitable in alternating current mains in star circuit withneutral wire, the filament being joined on the one hand to the neutralwire and on the other to a mains phase via a winding section of thecurrent limiting choke, which section is in series with said phase,while 'the discharge lamp together with its ap- States atent purtenantwinding section of the current limiting choke is supplied from twodifferent phases.

In mains with voltages of less than 220 volts, it is necessary foreconomic operations of the discharge lamp to transform the voltage tothis economic operating value by means of a leakage-reactancetransformer. When such leakage-reactance transformers are used, thecircuits are magnetically coupled at the stabilizing impedance accordingto the invention in such a way that the stabilizing impedance, whichconsists of several winding sections, is loosely coupled magneticallyvia so-called stray yokes to the series field of the primary coil afterthe fashion of a leakage-reactance transformer.

A few typical embodiments of the invention are illustrated by way ofexample in the attached drawing, in which:

Figs. 1, 2 and 5 each show a mixed light lamp for general lightingpurposes, such as have been disclosed for instance in U. S. Patent No.2,669,676.

Figs. 3 and 4 each show a circuit layout according to the presentinvention.

Figs. 6 and 7 are two further mixed light lamps;

Figs. 8 and 9 are two examples of the inductance circuit.

The electric lamp for mixed light shown in Figure 1 includes alight-transmitting sealed envelope: G which is filled with an inert gasunder pressure. Conducting means or terminals C extend through theenvelope G and are connected with the filament W for incandescent light.The second envelope G is located within the envelope G and is filledwith mercury vapor under pressure which is higher than the pressure ofthe inert gas in the envelope G Other conducting means or terminals Cextend through the envelope G and are connected with electrode means E,so that mercury vapor light is produced upon energization of theterminals C In accordance with the present invention, the deviceincludes two inductive circuit means, which, in the embodiment shown inFigure 1, include winding sections A and B, respectively, of a currentlimiting choke. The section A is connected in series to the terminals Cand the section B is connected in series to the terminals C The sectionsA and B are inductively coupled to reduce the initial voltage appearingat the filament W due to the high current flowing through the envelope Gfilled with mercury vapor, immediately upon energization of the filamentW The arrangements of Figs. 1, 2 and 5 differ in detail in that in Figs.1 and 5 the winding sections (AB) of a current limiting choke are joinedtogether in series after the fashion of an economy circuit and areconnected to a single phase.

In Fig. 2 the winding sections (A-B) of a current limiting choke areelectrically separated after the fashion of a pure transformationcircuit so that the filament in series with one Winding section (A) isconnected on the one hand to a phase and on the other to the neutralWire, while the discharge lamp, which is in series with the wind ingsection (B), is supplied from two mains phases.

Unlike Figs. 1, 2 and 5, Figs. 3 and 4 merely represent circuit layouts,the discharge lamp and the filament being only diagrammaticallyillustrated. In contradistinction to Figs. 1 and 5, the stabilizingimpedance in these two circuit layouts is magnetically loosely coupledvia so called stray yokes to the series field of the dielectricallyrigid primary coil after the fashion of a leakage-reactance transformer.This circuit becomes necessary if the maximum mains voltage available isless than 220 volts.

In the arrangement according to Fig. 3, the mains coil of the seriesfield of the leakage-reactance transformer is directly connected to themains, while the mains coil of the series field of the.leakage-reactance transformer according to Fig. 4 is connected in seriesto that winding section of the stabilizing impedance which is at thesame time in series with the filament.

Fig. 5 of the drawing illustrates a typical embodiment of an electriclamp for mixed light, which is preferably intended for general lightingpurposes and, as is diagrammatically shown, is connected to a straychoke. One end of the glow-lamp element is connected to a tapping pointZ of the series. unit. If, after the fashion of an autocircuit, the endof the winding section A is joined to the start of the winding section Band the filament W is joined to this connection-tapping point Z thecurrents of both elements will flow through the winding section A, whichis illustrated by the heavier lines. This auto or economy circuit canonly be applied if a lamp provided with three-pole connector is operatedon single-phase. The same end can also be achieved with the aid of aseries unit having separate windings. The separation of the windings isnecessary if the two elements have to be operated out-of-phase, forinstance, if the filament has to be connected between phase and neutralwire, and the electric arc to two phases in the interests of betteroperation.

The effect is as follows: Immediately after the lamp is switched on andthe electric arc ignited, the operating voltage of the electric arcdrops, as is well known, to a few volts; the rest of the no-load voltageis at the choke; the specific voltage drop in volts per winding of theseries unit is large during this period so that the partial voltageoccurring between the choke input and the tapping point is also large.The potential value of this partial voltage has, if the windings arearranged in the same direction, a subtracting etfect on the voltage ofthe filament. If the voltage rises owing to the pressure increase in theburner and the lamps main vessel, the voltage drops via the choke, i.e.via the Winding section to which the filament is connected. The partialvoltage to be subtracted consequently decreases, or the operatingvoltage remaining in the filament increases. The synchronous increase ofvoltage and vapor pressure of the lamp is of great importance becausethis will ensure that the temperature of the filament is kept at leastapproximately constant. A further advantage worthy of mention isachieved by the circuit described, in that the electric arc is virtuallyno longer extinguished on passing through the zero point because theseries unit acts as a leakage-reactance transformer and maintains analbeit strongly diminished fiow of current by the tapping of an ohmicresistance in the period during which the burners current changes itsdirection.

Fig. 8 illustrates diagrammatically a mixed light lamp with series unit,which lamp has two electric arcs and is operated with two phases. Themixed light lamps are shown merely symbolically and are marked ML.

Two standard burners can also be provided here in place of the twoelectric arcs accommodated in one bulb. The unit operates with twophases of power supply mains. When the lamp is first switched on, thevoltage at the electric arcs is again very small, so that there is acorrespondingly high voltage at the windings B. By poling the windings Aaccordingly, the magnetic flows produced can be made to counteract eachother and thus cause the voltages to be subtracted. This, however, hasthe result that the voltage at the circular-coil filament is less thanthe mains voltage to begin with. As the pressure in the discharge vesselincreases, and the voltage at the electric arcs rises and that at thewindings B falls accordingly, the choking action exerted on the windingsA also slackens so that after a while almost the full voltage appears atthe circular-coil filament.

Fig. 9 shows a similar arrangement for single-phase operation. In thesupply line here there is a transformer RT which may serve to keep thevoltage automatically constant, but which may also be used to change thecolour of the. radiated light by altering the voltage.

A mixed light lamp produced for projection purposes, i.e. a lamp with asuper high pressure burner and a circular-coil grid stretched over oneplane, has the great drawback that the directed light resultingintrinsically from the construction and designed for the illumination ofa light field reveals extremely substantial deviations in thecomposition of the light. In the centre of the luminous beam the lightmixture consisting of mercury, vapor and electric arc is predominant sothat a discoloration in the most important region of the picture isinevitable. This disadvantage is remedied or reduced to reasonableproportions also by widening the concentrated electric are into a lightspot. This enlargement of the arc can be achieved, to a certain extent,by shaping the burner accordingly, i.e. by giving the burner a fiat ovalshape in the section transverse to the burner axis. It has been shown,however, that it is virtually impossible to combat the local overloadingof the vessel wall caused thereby with other means, in order that theabsolutely essential high arc concentration can be maintained, whileensuring a reasonably long useful life. These difiiculties are overcomeby providing two or more electric arcs in one and the same burnervessel. Since, in the case of super high pressure burners, the light arestarts by being slender at the lower electrode and then, because of thegreater heat concentration, becomes bushy at the opposite, upperelectrode, the focal spot has the form. of a droplet tapering towardsthe bottom. By utilizing this structure, a square or rectangular focalspot can be obtained by providing two electric arcs which burn, at thetop, on an electrode common to both arcs and at the bottom on separateelectrodes. The V-shape of such an electric arc may also be balanced inrespect of light intensity by correcting the circular-coil gridaccordingly. This can be done in a simple manner by giving the circularcoil the V-shape as well, but arranging it inversely to the burner.

Figs. 6 and 7 illustrate typical embodiments drawn partially in section.The burner G of which a view is shown in Fig. 6, can only be designedfor the maintenance of a discharge path having a flat oval crosssectionand extending transversely to the burners axis, but may also representthe lateral elevation of the lamp according to Fig. 7. Similarly, threeelectrodes could also be sealed in at the bottom in order to producethree discharge paths. In this case, it would be advantageous to choosethe central axis of symmetry for the third path. Obviously a star oreven a delta layout could also be provided in the same way, thus alsopermitting a two-phase alternating current operation. For certainpurposes even a three-phase system might offer quite considerableadvantages. Fig. 8 illustrates a lamp of this type designed for lightprojection. The electric arcs to be produced between the main electrodeE and the secondary electrodes E and E form a raised V, while the middletwo arms of the circular coil grid W represent the inverse V-shape innormal position. The layout of the circular-coil grid illustratedcorresponds to a considerable extent to the topping-up factor necessaryfor the. production of a focal spot dispensing light evenly inpractically every direction, which is of very great importance.

As Figs. 5, 6 and 7 show, the lamps main vessel G is designed with anexpansion chamber EK projecting into the surrounding air and designed tocontrol the pressure of the gas-metal-vapor composition of said vesselin the event of said pressure rising too high. This chamber (EK) servesas a pressure governor as the internal pressure of the high-percentagemetal-vapor content of the gas-metal atmosphere is almost entirely dependent on the coldest point of the vessel. This obviates too great anincrease in the mains voltage (excessive voltage) which, as is wellknown, increases more than proportionally to the rate of power input andconsequently may lead to heat emissions which might cause a quiteconsiderable increase in the vapor pressure. The pressure of the lampsmain vessel, however, should be defined within wide limits by thesurrounding atmosphere. The

shape and dimensions of said vessel will depend on local conditions oron the lamps application. The use of this expansion vessel to centre andsupport the lamp construction is only of secondary importance. In lampsdesigned in this way the metal base body MB condenses in the expansionchamber. In addition, a residue which is not evaporated in stationaryoperation remains on the wall of the expansion chamber.

The expansion chamber EK is at the same time a safety valve as its wallis intentionally weakened.

Having now particularly described and ascertained the nature of my saidinvention and in what manner same is to be performed, I declare thatwhat I claim is:

1. An electric lamp for mixed light, comprising a main sealed envelopehaving a light-transmissive wall, a pressure-exerting inert gas fillingsaid envelope, conducting means extending through said wall of theenvelope, a filament for incandescent light, said filament being locatedwithin said envelope and being connected to said conducting means,another envelope having a light-transmitting wall, pressure-exertingmercury vapor filling the second-mentioned envelope, the pressure ofmercury vapor in the second-mentioned envelope being higher than thepressure of inert gas in the first-mentioned envelope, other conductingmeans extending through the wall of the second-mentioned envelope,electrode means connected with the second-mentioned conducting means forproducing mercury vapor light upon energiaztion of the second-mentionedconducting means, an inductive circuit means connected in series withthe first-mentioned conducting means, another inductive circuit meansconnected in series with the second-mentioned conducting means, said twoinductive circuit means being inductively coupled to reduce initial highvoltage appearing at the filament upon energization of said filament dueto the high current flowing through the mercury vapor-filledsecondmentioned envelope.

2. A lamp in accordance with claim 1, wherein said two inductive circuitmeans are interconnected in series.

3. A lamp in accordance with claim 1, wherein the second-mentionedconducting means consist of three terminals and said electrode meansconsist of three electrodes connected to the three terminals to providetwo mercury vapor arcs which burn in the form of a V.

References Cited in the file of this patent UNITED STATES PATENTS2,103,034 Inman Dec. 21, 1937 2,135,719 Krefft Nov. 8, 1938 2,153,036Burt Apr. 4, 1939 2,263,171 Hays Nov. 18, 1941

